Cloyster

Cloyster is a Pokemon with coverage limited to STAB moves and Normal-type attacks, yet despite this, it has access to one of the most diverse toolsets in RBY OU. Through the use of Clamp, Cloyster can provide free switches to its teammates while also walling some of the most prominent physical threats, such as Snorlax, particularly those running Reflect, and Tauros. It possesses a reasonably powerful Blizzard, with the ability to threaten freeze on special walls, and has the option of using Explosion on Starmie to set up a Rhydon or Tauros sweep. Its part-Ice typing gives it immunity to freeze and STAB on Blizzard, at the expense of being weaker to Rock Slide. However, Cloyster has some drawbacks that stop it from being one of the top threats of RBY OU. Firstly, not being a Normal-type means it can be paralyzed by Body Slam, unlike Chansey or Snorlax. Secondly, Clamp's subpar accuracy could prove deadly to Cloyster's pretensions, especially if it's paralyzed. Lastly, it needs to rely on Rest as means of recovery, which means it's going to remain completely passive for three turns whenever it wants to recover HP.